Table 6.

Summary of the mutations to the thioether bridge constituent, the seventh His and the disulfide bonds: effects on PPOs′ copper content and diphenolase/monophenolase activity. The modification of copper content and the activities are described compared to the wild type of the corresponding enzymes.

Thioether bridge constituent
Enzyme	Mutant	Diphenolase activity	Monophenolase activity	Copper %	Ref.
AoTYR[b]	Cys92Ala	n.i.	−33‐fold (l‐tyrosine: 1.8 s−1)	n.i.	[80]
AoTYR[a]	Cys82Ala	n.d. (l‐DOPA)	n.d. (l‐tyrosine)	60	[56]
CgAUS	Cys97Ala	n.d. (butein and fisetin) −7845‐fold (4‐tert‐butylcatechol: 16 μmol/(l x min))	n.i.	100	[53]
	Cys97Ala	−95‐fold (dopamine: 5.84 s−1)	++ (tyramine: 0.14 s−1)	42	[45]
	Cys97Ser	−37‐fold (dopamine: 15 s−1)	++ (tyramine: 0.55 s−1)	59
	Cys97Asp	−350‐fold (dopamine: 1.54 s−1)	++ (tyramine: 0.07 s−1)	53
	Cys97Asn	−450‐fold (dopamine: 1.24 s−1)	++ (tyramine: 0.05 s−1)	46
	Cys97Gly	−13‐fold (dopamine: 43 s−1)	++ (tyramine: 0.12 s−1)	34
Seventh histidine (7th His)
HsTYR	His389Ala	n.d.	n.d.	0	[54]
	His389Ala	+1.1‐fold (l‐DOPA: 38.4 s−1)	∼same (l‐tyrosine: 0.63 s−1)	n.i.	[55]
CgAUS	His285Ala	−38‐fold (dopamine: 14.7 s−1)	n.d. (tyramine)	23	[45]
AoTYR[a]	His332Asn	n.d. (l‐DOPA)	n.d. (l‐tyrosine)	40	[56]
Disulfide bonds (S−S)
CgAUS	Cys31Ala	n.d. (dopamine)	n.d. (tyramine)	n.i.	[45]
	Cys32Ala	n.d. (dopamine)	n.d. (tyramine)	n.i.
DmproPO	Cys586Ser	−2.5‐fold (dopamine: 5752 s−1)	n.i.	n.i.	[83]
	Cys588Ser	−2.7‐fold (dopamine: 5333 s−1)	n.i.	n.i.
	Cys586Ala‐Cys588Ala	−3.1‐fold (dopamine: 4595 s−1)	n.i.	n.i.
	Cys586Ser‐Cys588Ser	−2.4‐fold (dopamine: 5958 s−1)	n.i.	n.i.

[a] Refers to AoTYR (mel0‐Q00234). [b] Refers to AoTYR (melB‐Q2UP46). n.d.: no detected activity, n.i.: no information from the particular study, ++: generation of monophenolase activity that was not present in the wild type, entries with μmol/(l×min) refer to volumetric activity and those with s^‐1 give the k_cat value.